Activation of endothelial nitric oxide synthase is dependent on its interaction with globular actin in human umbilical vein endothelial cells

Rapid shear stress-dependent ENaC membrane insertion is mediated by the endothelial glycocalyx and the mineralocorticoid receptor

The contribution of the shear stress-sensitive epithelial Na⁺ channel (ENaC) to the mechanical properties of the endothelial cell surface under (patho)physiological conditions is unclear. This issue was addressed in in vivo and in vitro models for endothelial dysfunction. Cultured human umbilical vein endothelial cells (HUVEC) were exposed to laminar (LSS) or non-laminar shear stress (NLSS). ENaC membrane insertion was quantified using Quantum-dot-based immunofluorescence staining and the mechanical properties of the cell surface were probed with the Atomic Force Microscope (AFM) in vitro and ex vivo in isolated aortae of C57BL/6 and ApoE/LDLR^-/- mice. Flow- and acetylcholine-mediated vasodilation was measured in vivo using magnetic resonance imaging. Acute LSS led to a rapid mineralocorticoid receptor (MR)-dependent membrane insertion of ENaC and subsequent stiffening of the endothelial cortex caused by actin polymerization. Of note, NLSS stress further augmented the cortical stiffness of the cells. These effects strongly depend on the presence of the endothelial glycocalyx (eGC) and could be prevented by functional inhibition of ENaC and MR in vitro endothelial cells and ex vivo endothelial cells derived from C57BL/6, but not ApoE/LDLR^-/- vessel. In vivo In C57BL/6 vessels, ENaC- and MR inhibition blunted flow- and acetylcholine-mediated vasodilation, while in the dysfunctional ApoE/LDLR^-/- vessels, this effect was absent. In conclusion, under physiological conditions, endothelial ENaC, together with the glycocalyx, was identified as an important shear stress sensor and mediator of endothelium-dependent vasodilation. In contrast, in pathophysiological conditions, ENaC-mediated mechanotransduction and endothelium-dependent vasodilation were lost, contributing to sustained endothelial stiffening and dysfunction.

Regulation of Endothelial Nitric Oxide Synthase in the Reticular Lamina of the Organ of Corti by a Nitric Oxide Donor

In the vertebrate cochlea, the reticular lamina seals the organ of Corti against the endolymph filled scala media. After noise exposure, fast alterations in the endothelial nitric oxide synthase (eNOS) expression level were identified in this cochlear structure. Minor amounts of nitric oxide (NO) produced by eNOS or applied by NO donors such as S-nitroso-N-acetyl-penicillamine (SNAP) might protect this vulnerable part of the organ of Corti, on the line of gap junctions of supporting cells and cochlear microcirculation. In n=5 anesthetized guinea pigs, SNAP was intravenously applied in two concentrations. Six untreated animals served as controls. The cochleae were removed and prepared for immunoelectron microscopy using specific gold-labeled anti-eNOS antibodies. The density of the gold particles was quantified for seven cellular regions in the reticular lamina at the ultrastructural level. Following SNAP application, a significant increase in eNOS expression (+176%) was detected compared with controls (p=0.012). The increase occurred mainly in actin-rich cuticular structures and the prominent microtubules bundles. Correlation analysis revealed three clear and five moderate cellular associations for controls, whereas only one clear and one moderate after SNAP application. Thus, application of the NO donor SNAP resulted in an increase in eNOS expression in distinct regions of the reticular lamina.

Cytonemes Versus Neutrophil Extracellular Traps in the Fight of Neutrophils with Microbes

Neutrophils can phagocytose microorganisms and destroy them intracellularly using special bactericides located in intracellular granules. Recent evidence suggests that neutrophils can catch and kill pathogens extracellularly using the same bactericidal agents. For this, live neutrophils create a cytoneme network, and dead neutrophils provide chromatin and proteins to form neutrophil extracellular traps (NETs). Cytonemes are filamentous tubulovesicular secretory protrusions of living neutrophils with intact nuclei. Granular bactericides are localized in membrane vesicles and tubules of which cytonemes are composed. NETs are strands of decondensed DNA associated with histones released by died neutrophils. In NETs, bactericidal neutrophilic agents are adsorbed onto DNA strands and are not covered with a membrane. Cytonemes and NETs occupy different places in protecting the body against infections. Cytonemes can develop within a few minutes at the site of infection through the action of nitric oxide or actin-depolymerizing alkaloids of invading microbes. The formation of NET in vitro occurs due to chromatin decondensation resulting from prolonged activation of neutrophils with PMA (phorbol 12-myristate 13-acetate) or other stimuli, or in vivo due to citrullination of histones with peptidylarginine deiminase 4. In addition to antibacterial activity, cytonemes are involved in cell adhesion and communications. NETs play a role in autoimmunity and thrombosis.

Endothelial Nanomechanics in the Context of Endothelial (Dys)function and Inflammation

SIGNIFICANCE

Stiffness of endothelial cells is closely linked to the function of the vasculature as it regulates the release of vasoactive substances such as nitric oxide (NO) and reactive oxygen species. The outer layer of endothelial cells, consisting of the glycocalyx above and the cortical zone beneath the plasma membrane, is a vulnerable compartment able to adapt its nanomechanical properties to any changes of forces exerted by the adjacent blood stream. Sustained stiffening of this layer contributes to the development of endothelial dysfunction and vascular pathologies. Recent Advances: The development of specific techniques to quantify the mechanical properties of cells enables the detailed investigation of the mechanistic link between structure and function of cells.

CRITICAL ISSUES

Challenging the mechanical stiffness of cells, for instance, by inflammatory mediators can lead to the development of endothelial dysfunction. Prevention of sustained stiffening of the outer layer of endothelial cells in turn improves endothelial function.

FUTURE DIRECTIONS

The mechanical properties of cells can be used as critical marker and test system for the proper function of the vascular system. Pharmacological substances, which are able to improve endothelial nanomechanics and function, could take a new importance in the prevention and treatment of vascular diseases. Thus, detailed knowledge acquisition about the structure/function relationship of endothelial cells and the underlying signaling pathways should be promoted.

Potential Pathways Involved in Elaidic Acid Induced Atherosclerosis in Human Umbilical Vein Endothelial Cells

Researches have demonstrated that trans-fatty acids are related to the progression of atherosclerosis, but the underlying mechanism is not clear till now. In the presented study, two-dimensional electrophoresis based proteomics was used to discover the role of elaidic acid in atherosclerosis. In human umbilical vein endothelial cells (HUVEC), twenty-two and twenty-three differentially expressed proteins were identified in low (50 μmol/L) and high (400 μmol/L) concentration elaidic acid simulated groups, respectively, comparing with the control group. The expressions of some selected proteins (PSME3, XRCC5, GSTP1, and GSTO1) were validated by qRT-PCR analysis. Western blotting analysis further confirmed that elaidic acid downregulated the expression of PSME3and XRCC5. Moreover, P53, the downstream protein of PSME3, was further investigated. Results demonstrated that a variety of proteins, many of which were related to oxidative stress, apoptosis, and DNA damage, were involved in the elaidic acid induced atherosclerosis. Furthermore, P53 was demonstrated to regulate the atherosclerosis through cell cycle arrest and apoptosis pathway.

Hydrogen Sulfide Induces Keap1 S-sulfhydration and Suppresses Diabetes-Accelerated Atherosclerosis via Nrf2 Activation

Hydrogen sulfide (H2S) has been shown to have powerful antioxidative and anti-inflammatory properties that can regulate multiple cardiovascular functions. However, its precise role in diabetes-accelerated atherosclerosis remains unclear. We report here that H2S reduced aortic atherosclerotic plaque formation with reduction in superoxide (O2 (-)) generation and the adhesion molecules in streptozotocin (STZ)-induced LDLr(-/-) mice but not in LDLr(-/-)Nrf2(-/-) mice. In vitro, H2S inhibited foam cell formation, decreased O2 (-) generation, and increased nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and consequently heme oxygenase 1 (HO-1) expression upregulation in high glucose (HG) plus oxidized LDL (ox-LDL)-treated primary peritoneal macrophages from wild-type but not Nrf2(-/-) mice. H2S also decreased O2 (-) and adhesion molecule levels and increased Nrf2 nuclear translocation and HO-1 expression, which were suppressed by Nrf2 knockdown in HG/ox-LDL-treated endothelial cells. H2S increased S-sulfhydration of Keap1, induced Nrf2 dissociation from Keap1, enhanced Nrf2 nuclear translocation, and inhibited O2 (-) generation, which were abrogated after Keap1 mutated at Cys151, but not Cys273, in endothelial cells. Collectively, H2S attenuates diabetes-accelerated atherosclerosis, which may be related to inhibition of oxidative stress via Keap1 sulfhydrylation at Cys151 to activate Nrf2 signaling. This may provide a novel therapeutic target to prevent atherosclerosis in the context of diabetes.

Markers of early endothelial dysfunction in intrauterine growth restriction-derived human umbilical vein endothelial cells revealed by 2D-DIGE and mass spectrometry analyses

Intrauterine growth restriction (IUGR) associates with fetal and placental vascular dysfunction, and increased cardiovascular risk later on life. We hypothesize that endothelial cells derived from IUGR umbilical veins present significant changes in the proteome which could be involved in the endothelial dysfunction associated to this conditions. To address this the proteome profile of human umbilical endothelial cells (HUVEC) isolated from control and IUGR pregnancies was compared by 2D-Differential In Gel Electrophoresis (DIGE) and further protein identification by MALDI-TOF MS. Using 2D-DIGE 124 spots were identified as differentially expressed between control and IUGR HUVEC, considering a cut-off of 2 fold change, which represented ∼10% of the total spots detected. Further identification by MALDI-TOF MS and in silico clustering of the proteins showed that those differentially expressed proteins between control and IUGR HUVEC were mainly related with cytoskeleton organization, proteasome degradation, oxidative stress response, mRNA processing, chaperones and vascular function. Finally Principal Component analysis of the identified proteins showed that differentially expressed proteins allow distinguishing between control and IUGR HUVEC based on their proteomic profile. This study demonstrates for the first time that IUGR-derived HUVEC maintained in primary culture conditions present an altered proteome profile, which could reflect an abnormal programming of endothelial function in this fetal condition.

Emerging role of hydrogen sulfide in hypertension and related cardiovascular diseases

Hydrogen sulfide (H2 S) has traditionally been viewed as a highly toxic gas; however, recent studies have implicated H2 S as a third member of the gasotransmitter family, exhibiting properties similar to NO and carbon monoxide. Accumulating evidence has suggested that H2 S influences a wide range of physiological and pathological processes, among which blood vessel relaxation, cardioprotection and atherosclerosis have been particularly studied. In the cardiovascular system, H2 S production is predominantly catalyzed by cystathionine γ-lyase (CSE). Decreased endogenous H2 S levels have been found in hypertensive patients and animals, and CSE(-/-) mice develop hypertension with age, suggesting that a deficiency in H2 S contributes importantly to BP regulation. H2 S supplementation attenuates hypertension in different hypertensive animal models. The mechanism by which H2 S was originally proposed to attenuate hypertension was by virtue of its action on vascular tone, which may be related to effects on different ion channels. Both H2 S and NO cause vasodilatation and there is cross-talk between these two molecules to regulate BP. Suppression of oxidative stress may also contribute to antihypertensive effects of H2 S. This review also summarizes the state of research on H2 S and hypertension in China. A better understanding of the role of H2 S in hypertension and related cardiovascular diseases will allow novel strategies to be devised for their treatment.

Bidirectional cross-regulation between the endothelial nitric oxide synthase and β-catenin signalling pathways

AIMS

β-catenin has been shown to be regulated by inducible nitric oxide synthase (NOS) in endothelial cells. We investigated here whether β-catenin interacts with and regulates endothelial NOS (eNOS) and whether eNOS activation promotes β-catenin signalling.

METHODS AND RESULTS

We identified β-catenin as a novel eNOS binding protein in human umbilical vein endothelial cells (HUVECs) by mass spectroscopy and western blot analyses of β-catenin and eNOS immunoprecipitates. This was confirmed by in situ proximity ligation assay. eNOS activity, assessed by cGMP production and eNOS phosphorylation (Ser1177), was enhanced in β-catenin(-/-) mouse pulmonary endothelial cells (MPECs) relative to wild-type MPECs. eNOS activation (using adenosine, salbutamol, thrombin, or histamine), or application of an NO donor (spermine NONOate) or cGMP-analogue (8-bromo-cGMP) caused nuclear translocation of β-catenin in HUVEC as shown by western blotting of nuclear extracts. Exposure to spermine NONOate, 8-bromo-cGMP, or sildenafil (a phosphodiesterase type 5 inhibitor) also increased the expression of β-catenin-dependent transcripts, IL-8, and cyclin D1. Stimulation of wild-type MPECs with basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), spermine NONOate, 8-bromo-cGMP, or sildenafil increased tube length relative to controls in an angiogenesis assay. These responses were abrogated in β-catenin(-/-) MPECs, with the exception of that to bFGF which is NO-independent. In C57BL/6 mice, subcutaneous VEGF-supplemented Matrigel plugs containing β-catenin(-/-) MPECs exhibited reduced angiogenesis compared with plugs containing wild-type MPECs. Angiogenesis was not altered in bFGF-supplemented Matrigel.

CONCLUSION

These data reveal bidirectional cross-talk and regulation between the NO-cGMP and β-catenin signalling pathways.

Regulation of endothelial nitric oxide synthase activity by protein-protein interaction

Endothelial nitric oxide synthase (eNOS) is expressed in vascular endothelial cells and plays an important role in the regulation of vascular tone, platelet aggregation and angiogenesis. Protein-protein interactions represent an important posttranslational mechanism for eNOS regulation. eNOS has been shown to interact with a variety of regulatory and structural proteins which provide fine tuneup of eNOS activity and eNOS protein trafficking between plasma membrane and intracellular membranes in a number of physiological and pathophysiological processes. eNOS interacts with calmodulin, heat shock protein 90 (Hsp90), dynamin-2, β-actin, tubulin, porin, high-density lipoprotein (HDL) and apolipoprotein AI (ApoAI), resulting in increases in eNOS activity. The negative eNOS interacting proteins include caveolin, G protein-coupled receptors (GPCR), nitric oxide synthase-interacting protein (NOSIP), and nitric oxide synthase trafficking inducer (NOSTRIN). Dynamin-2, NOSIP, NOSTRIN, and cytoskeleton are also involved in eNOS trafficking in endothelial cells. In addition, eNOS associations with cationic amino acid transporter-1 (CAT-1), argininosuccinate synthase (ASS), argininosuccinate lyase (ASL), and soluble guanylate cyclase (sGC) facilitate directed delivery of substrate (L-arginine) to eNOS and optimizing NO production and NO action on its target. Regulation of eNOS by protein-protein interactions would provide potential targets for pharmacological interventions in NO-compromised cardiovascular diseases.

Estradiol effects on intracellular Ca(2+) homeostasis in bovine brain-derived endothelial cells

Estrogens diversely affect various physiological processes by genomic or non-genomic mechanisms, in both excitable and non-excitable cells. Additional to the trophic effects of estrogens promoting cell growth and differentiation, recent experimental evidence highlights their involvement in the regulation of intracellular Ca(2+) homeostasis. The effects of estrogens on excitable cells are well documented. However, these steroids also influence numerous physiological events in non-excitable cells, such as fibroblasts or vascular endothelial cells. We have focused our attention on an immortalized endothelial-like cell line derived from fetal bovine cerebellum. Estradiol (E(2)) effects on intracellular Ca(2+) homeostasis were tested by varying the exposure time to the hormone (8, 24, 48 h). Calcium measurements were performed with genetically encoded Ca(2+) probes (Cameleons) targeted to the main subcellular compartments involved in intracellular Ca(2+) homeostasis (cytosol, endoplasmic reticulum, mitochondria). Mitochondrial Ca(2+) uptake significantly decreased after 48-h exposure to E(2), whereas cytosolic and endoplasmic reticulum responses were unaffected. The effect of E(2) on mitochondrial Ca(2+) handling was blocked by ICI 182,780, a pure estrogen receptor antagonist, suggesting that the effect was estrogen-receptor-mediated. To evaluate whether the decrease of Ca(2+) uptake affected mitochondrial membrane potential (ΔΨm), cells were monitored in the presence of tetra-methyl-rhodamine-methylester; no significant changes were seen between cells treated with E(2) and controls. To investigate a mechanism of action, we assessed the possibile involvement of the permeability transition pore (PTP), an inner mitochondrial membrane channel influencing energy metabolism and cell viability. We treated cells with CyclosporinA (CsA), which binds to the matrix chaperone cyclophilin-D and regulates PTP opening. CsA reversed the effects of a 48-h treatment with E(2), suggesting a possible transcriptional modulation of proteins involved in the mitochondrial permeability transition process.

Beyond antiangiogenesis: vascular modulation as an anticancer therapy-a review

This review attempts to move beyond the traditional borders of antiangiogenesis and toward the dynamic, evolving strategies of vascular modulation. This repositioning entails a two-fold paradigm shift: conceptually, to a view of antiangiogenesis as only one part of a larger story, and therapeutically, to approaches which attempt to modulate tumor blood flow instead of simply inhibiting it. Three vascular modulation strategies-provascular, antivascular, and redistributive-are presented with representative compounds. These vascular modulation strategies are described in specific measurable characteristics (blood vessel maturity and type, effect on blood flow, microenvironmental target, molecular target, angiogenic biomarker, and imaging biomarkers) that will help define the tumor types that are more susceptible to a particular vascular modulation strategy thereby guiding therapeutic agent selection and enabling a personalized medicine approach.